William and Kate celebrate a newborn baby boy, as world celebrates future king

THE United Kingdom has welcomed a future king with the announcement that Prince William and Catherine have a new baby boy.

He was bo at 4.24pm local time (1.24am AEST) and weighs 8lbs 6oz or 3800 grams.

William was present at the birth.

No name has been announced.

The news was announced in traditional fashion with a notice at Buckingham Palace.

Clarence House announced that \"The Queen, The Duke of Edinburgh, The Prince of Wales, The Duchess of Cowall, Prince Harry and families have been told and are delighted.\"

Like the late Princess Diana before her, Catherine, 31, gave birth in a private suite at St Mary's Hospital in London.

The birth announcement - a signed proclamation by her doctors - was then driven to the Palace and displayed on an easel.

The most anticipated royal birth since Prince William himself was bo on June 21, 1982 will be celebrated across the Commonwealth.

As the couple's first child, the baby is destined to become head of the world's most famous monarchy, but he/she will have a commoner's start to life as Catherine plans to spend six weeks with her family after leaving hospital.

It's reported she will tu to mum Carole Middleton, a mother of three, for help in the first few weeks.

Proud dad Prince William is understood to have two weeks' pateity leave from his job as a search-and-rescue pilot with the RAF.